16 lessons in astronomy.

The course

A course through this app in the order a class would take it: the sky first, then the Solar System, the stars, the galaxies, the universe, and the question of life. Each lesson is a short path of readings and things to look at. Follow it straight through, or wander off and come back; the checkmarks remember where you have been.

Each stop opens the app itself: a world to visit, a star or a galaxy at its real place in your sky, a chapter to read, a view to try. Tonight says when a lesson's subject is up: “Tonight’s lesson”, and where to look.

The sixteen lessons

1. Looking up: the sky and how it moves Free
   Why the stars wheel overhead, why they change with the season, and how to read the sky with your own eyes.
2. Sun, Moon and the calendar Free
   Phases, eclipses, seasons and the zodiac: the sky as the first clock and calendar.
3. Light and telescopes Free
   Almost everything we know arrived as light. How it is gathered, split, and read.
4. The Solar System as a family
   Where the Sun and planets came from, what holds them together, and what was left over.
5. The rocky worlds
   Mercury, Venus, Earth and Mars: four planets from the same disc, four different fates.
6. The giants and their moons
   Jupiter, Saturn, Uranus and Neptune, and the moons that turned out to be worlds in their own right.
7. The edge: Pluto, Charon and the Kuiper belt
   The cold outer Solar System, and why Pluto is what it is.
8. The Sun as a star
   What makes the Sun shine, its weather, and how it will end.
9. What a star is
   Mass, temperature, color and brightness, and the diagram that sorts every star.
10. Star birth, clusters and nebulae
    Where stars come from, and the nurseries and families they leave behind.
11. Star death
    Red giants, planetary nebulae, supernovae, and what is left: white dwarfs, neutron stars and black holes.
12. The extreme universe
    Gravity, density and speed turned far past anything on Earth: dead stars that spin like lighthouses, the strongest magnets known, black holes feeding and firing jets, and the ripples in space when two of them collide.
13. The Milky Way and other galaxies
    Our galaxy from the inside, the kinds of galaxies there are, and the neighbors we are bound to.
14. The universe: expansion, dark matter and the oldest light
    The Big Bang in plain words, the evidence for it, and the two dark mysteries that make up most of everything.
15. Other worlds: exoplanets and life
    How planets around other stars are found, what kinds there are, and whether anyone is home.
16. Going out to look
    Meteor showers, deep-sky objects and planning a night: the course ends under a real sky.

Where to find it

Open Explore and tap Lessons. The checkmarks remember where you have been, so you can wander off and come back.

What is free

The first three lessons are free: “Looking up: the sky and how it moves”, “Sun, Moon and the calendar”, “Light and telescopes”. The other 13 come with The Course, the pack that also holds The Whole Story and Kid Mode. Each pack is a one-time purchase inside the app, yours forever, not a subscription, with Family Sharing included; Everything is all three packs. If you bought Cosmic Expansion, you already own Everything.

For a class

The syllabus, and how a school puts the app on its iPads, are on the teachers’ page.

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